Static impedance relay

ABSTRACT

A static impedance relay for controlling a circuit includes a switch operated by a relay coil which is connected to a zero detector. The zero detector is fed with a first pulsating voltage which is proportional to the current supplied and a second voltage which is the algebraic sum of a direct voltage proportional to the voltage supply and a second pulsating voltage adjustably proportional to the voltage supply.

United States Patent 1 3,629,658

[72] inventors Anders Help; [50] Field of Search 317/36 D. Torkel Johansson, both ol Vasteras, 36 E; 335/7 Sweden [21 AppL 35,50 [56] References Clted [22] Filed May 7, 1970 UNITED STATES PATENTS [45] Patented Dec. 21, 1971 2,495,166 1/1950 Goldsborough 317/36 D 1 Asslsnee Allmnnl Swish Elektrish Akflebollsfl 3,543,092 1 1/1970 Hoel 317 36 D Vasteras, Sweden I [32] Priority 8, 1969 Primary Examiner-LT Hrx [33 1 Sweden Attorney-Jennings Bailey, Jr.

ABSTRACT: A static impedance relay for controlling a circuit [54] STATIC IMPEDANCE RELAY includes a switch operated by a relay coil which is connected to a zero detector. The zero detector is fed with a first pulsat- 4 Claims, 10 Drawing Figs.

mg voltage Wind] 18 proportional to the current supplied and a [52] US. Cl 317/36 I), second voltage which is the algebraic Sum of a direct vonage 317/36 E proportional to the voltage supply and a second pulsating volt- [51] lnt. Cl l'l0Z lL3/3 age adj-stably proportional to the voltage 34 W 1 17 as dsl i h iikh 36 -1L 4 I 6 r0 7 39 STATIC IMPEDANCE RELAY BACKGROUND OF THE INVENTION power lines, bus bars, transformers and generators, which are often constituted as measuring relays or as starting elements for other protection means.

2. The Prior Art Depending on the requirements of the circuitry, such relays in an RX plane may have different operating curves. The simplest operating curve is a circle with its center at the point of intersection of said plane. This circular curve is in many cases not very suitable since the relay may interpret functions, for instance when the object to be protected is heavily loaded, which may be understood by the relay as a decreasing impedance. This tendency of the relay can be eliminated to a great extent by allowing the operating curve to be elongated in a certain direction in the RX plane, which can be effected by means of more or less complicated circuits, for example with the help of a compensating impedance. There are also relays having elliptical or otherwise elongated operating curves to reduce the risks of unnecessary operation. The latter relays often have technically complicated circuits and relatively long operating times. High-speed relays usually have an unfavorable operating curve, for example relays having cloverleaf operating curves may be mentioned.

SUMMARY OF THE INVENTION The present invention relates to a static impedance relay having great possibilities of variation for the adjustment of various qualities, as well as having an extremely short operating time. The relay comprises a current circuit, a voltage circuit and a zero detector connected to both circuits, the current circuit being arranged to generate a pulsating voltage which is proportional to the current supplied. The invention is characterized in that the voltage circuit comprises a first circuit to generate a direct voltage which proportional to the voltage supplied and a second circuit to generate a second, pulsating voltage which is proportional to the voltage supplied, and a means to summate the two voltages.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, FIGS. 1 and 3 shown connection diagrams for two slightly different variations of the invention. FIG. 2a shows some examples of different operating curves which can be obtained with the connection according to FIG. 1. FIG. 2b shows how an oval operating curve has been turned in the impedance plane by known means. FIG. 4a shows a circular operating curve obtained with the connection according to FIG. 3. FIGS. 4b and 4c, respectively, show voltages from the current circuit and voltage circuit of the case shown in FIG. 4a. FIG. 5a shown a circular operating curve with displaced center point and FIGS. 5b and 5c shows the voltages from the current and voltage circuits respectively for the latter case.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment of the invention shown in FIG. 1 has a transformer l with primary winding 2 and secondary winding 3. The primary winding is connected by terminals 4 and 5 to the current transformer(s) of the object to be protected, and a current I flows through it. The ends of the secondary winding have connection terminals 6 and 7 also a number of extra outputs 8, 9, located between them, whereby the conversion ratio of the transformer can be varied. A rectifier bridge 10 is connected to the secondary winding and connected over the DC output of the bridge is a resistor 11 between the points 12 and 13. The part of the impedance relay described here forms the current circuit mentioned in the introduction.

The impedance relay according to the invention also has a voltage circuit including a second transformer with a primary winding 2land two secondary windings 22, 23. The primary winding 21 is connected by means of two terminals 24, 25 to the voltage transformer(s) of the object to be protected and is fed with the voltage U. The secondary winding 22'has two end terminals 26, 27 and also a central output 28.

Between the end terminals is inserted a phase-turning circuit consisting of a resistor 50 and a capacitor 51. The three outputs are connected bymeans of conduits 29, 30 and 31 to the center points 32, 33, 34, in individual branches of a rectifier connection 35. The positive pole of the rectifier connection is connected over a resistor 36 to a point 37 in the relay connection. The negative pole of the rectifier connection is connected to another point 38. A capacitor 39 is connected between the two poles of the rectifier connection to equalize any ripple voltage. A resistor 14 is connected between the points 37 and 38. The second secondary winding 23 has two end terminals 40 ad 41 and also a number of intermediate outputs 42 so that the voltage taken out from the winding 23 can be varied stepwise from zero to a maximum value. A rectifier bridge 43 has its AC outputs connected to the secondary winding whereas the DC outputs are connected over a resistor 44 to the end points of the resistor 14. A capacitor 45 may be connected in the feeding circuit to the rectifier bridge 43 if an alternation of the phase position is desired and thus an alteration of the operating conditions to the really.

The momentary value of the voltage between points 12 and 37 is sensed by a zero detector 15. This voltage consists of the difference between the voltage over the resistor 11, which is proportional to the current I, and the voltage over the resistor 14, which is proportional to he voltage U. The zero detector emits an output signal which closes the relay 17 when the temporary value of the voltage between the points 12 and 37 is greater than zero.

The rectifier connection 35 gives a direct voltage across the resistor 14 which is proportional to the voltage U. The current circuit produces over the resistor 11 a first pulsating direct voltage proportional to the current I. These two voltages give the impedance relay a circular operating curve which is shown by the circle 46 in FIG. 2a. This is assuming the voltage taken out from the secondary winding 23 is zero. If, on the other hand, a voltage is also taken out from the secondary winding 23, a second pulsating direct voltage obtained from the rectifier bridge 43 is supplied to the resistor 14, and the second pulsating voltage is added to the direct voltage from rectifier 35. The algebraic sum of these voltages circle 46 then becomes a substantially oval curve since the points at which it intersects the R-axis are moved closer to the point of intersection of the lines R and X. The convex curve parts 47 shown the appearance of the operating curve resulting from a relatively low value of the voltage taken out from the winding 23. At a higher value of the voltage, the operating curve will become a straight line 48 in the region nearest the R-axis, whereas, upon an even higher value of the voltage, the curve will become concave as shown at 49.

If a capacitor 45 is connected in the feeding circuit to the rectifier bridge 43, it is possible to turn the operating curve of the relay in the RX plane and FIG. 2a shows the appearance of the operating curve for a certain value of the voltage from the secondary winding 23 and a certain value of the capacitance of the capacitor 45.

The embodiment of the invention shown in FIG. 3 differs from that shown in FIG. 1 in two aspects. The rectifier bridge 10 in the current circuit is replaced by a one-way rectifier or valve 19 so that the voltage arising over the resistor 11 has the appearance shown in FIG. 4b. Also the rectifier bridge 43 is omitted so that the voltage arising across the resistor 14 is an alternating voltage insofar as any voltage is taken out from the secondary winding 223.

If no voltage is taken out from the secondary winding 23, the voltage arising across the resistor 14 is a direct voltage which is obtained from the rectifier connection 35 ad this voltage is shown in FIG. 4c. Under these circumstances the operating curve of the relay will be a circle with its center at the point of intersection of the lines R and X. If, on the other hand, and alternating voltage is taken out from the secondary winding 23 by connecting the resistor 14 to two the winding terminals 40, 41, 42, separated from each other, through a capacitor 52, the direct voltage from the rectifier connection 35 will be superimposed by an alternating voltage and the voltage arising over the resistor 14 acquires the appearance shown in FIG. 50. This voltage, together with the pulsating direct voltage from the resistor ll, shown in FIG. b, gives the relay the operating curve shown in FIG. 5a, that is, the circular curve is moved along the X-axis in its positive direction. By reversing the current from the winding 23 the curve is moved along the X-axis in the negative direction.

The voltage circuit achieved according to the invention thus makes it possible in an extremely simple manner to influence the operating curve of the relay in several respects so that the relay can be used for different purposes.

We claim:

1. Static impedance relay comprising a current circuit, a voltage circuit and a zero detector connected to both circuits, the current circuit including means to generate a first pulsating voltage which is proportional to the current supplied, the voltage circuit comprising a first circuit part including means to generate a direct voltage which is proportional to the voltage supplied and a second circuit part including means to generate a second pulsating voltage which is proportional to the voltage supplied, means to form the algebraic sum of the direct and second pulsating voltages, said zero detector connected to be responsive to the difference between the absolute values of said first pulsating voltage and said sum.

2. Impedance relay according to claim 1, the current circuit comprising a full-wave rectifier (l0), and the means for generating the second pulsating voltage comprising a fullwave rectifier (43).

3. Impedance relay according to claim 1, the current circuit comprising a half-wave rectifier (l9), and the means to generate the second pulsating voltage including means to generate an alternating voltage.

4. Impedance relay according to claim 1, in which the voltage circuit includes a voltage transformer (20) having a primary winding 21) and a first and a second secondary winding (22, 23), the first circuit part being connected to the first secondary winding and the second circuit part connected to the second secondary winding, the second secondary winding having a plurality of outputs (40, 41, 42) to adjust the desired amplitude of the second pulsating voltage. 

1. Static impedance relay comprising a current circuit, a voltage circuit and a zero detector connected to both circuits, the current circuit including means to generate a first pulsating voltage which is proportional to the current supplied, the voltage circuit comprising a first circuit part including means to generate a direct voltage which is proportional to the voltage supplied and a second circuit part including means to generate a second pulsating voltage which is proportional to the voltage supplied, means to form the algebraic sum of the direct and second pulsating voltages, said zero detector connected to be responsive to the difference between the absolute values of said first pulsating voltage and said sum.
 2. Impedance relay according to claim 1, the current circuit comprising a full-wave rectifier (10), and the means for generating the second pulsating voltage comprising a full-wave rectifier (43).
 3. Impedance relay according to claim 1, the current circuit comprising a half-wave rectifier (19), and the means to generate the second pulsating voltage including means to generate an alternating voltage.
 4. Impedance relay according to claim 1, in which the voltage circuit includes a voltage transformer (20) having a primary winding (21) and a first and a second secondary winding (22, 23), the first circuit part being connected to the first secondary winding and the second circuit part connected to the second secondary winding, the second secondary winding having a plurality of outputs (40, 41, 42) to adjust the desired amplitude of the second pulsating voltage. 